Study On Magnetic Separation Of Biomass Magnetic Roasting From Dabaoshan Iron Tailings

Iron is the largest and most widely used metal in China.In 2021,A total of 1.12 billion tons of iron ore and ore concentrate were imported to China.In the same year,841 million tons of iron tailings were produced in China.The utilization rate of iron tailings was only18.9%.A large number of iron tailings are not effectively utilized,which not only causes a large amount of land waste,but also causes a huge risk of leaching toxicity to the surrounding ecological environment.Therefore,an economic and environmental recovery process is urgently needed to recover iron resources in tailings.Magnetization roasting is considered as an effective way to recover iron resources from tailings.In this thesis,iron was effectively recovered by biomass magnetization roasting-third order magnetic separation process using plant biomass as reducing agent.The effects of roasting temperature,roasting time,biomass addition amount and other factors on magnetic roasting effect were investigated.X-ray fluorescence spectroscopy,scanning electron microscopy,X-ray diffractometer and vibrating sample magnetometer were used to characterize the chemical composition,surface morphology,phase structure and magnetic properties of iron tailings,roasted products and magnetite concentrate.Industrial analysis and elemental analysis were carried out to explore the mechanism of iron migration and transformation of magnetized roasting iron tailings.The main results are as follows:The occurrence of iron in Dabaoshan iron tailings is mainly in the form of hematite（Fe₂O₃）and a small amount of goethite（Fe O（OH））.Iron tailings particle structure is loose,particle size varies,fragmentary or flake,and the surface is accompanied by many particles,flake,block and other materials;The saturation magnetization（Ms）of iron tailings is only0.05emu/g,which cannot be recovered by magnetic separation.The content of C and H in each plant biomass is above 45%and 6%,respectively,indicating that reducing substances of each biomass can produce enough reducing gases to magnetize roasted iron tailings.The orthogonal experiment using eucalyptus chips as reducing agent showed that roasting temperature had the greatest effect on iron grade and iron recovery,and the roasting time and the addition amount of eucalyptus chips were far greater.Under the optimal conditions,the saturation magnetization（Ms）of iron tailings roasted with eucalyptus chips can be increased from 0.05 emu/g to 47.4emu/g of roasted products,and the saturation magnetization（Ms）of roasted products can be increased to 59.99 emu/g by high-medium-weak third-order wet magnetic separation.After roasting and magnetic separation,iron tailings have many pores and lamellar structures with smooth surface.The optimum conditions for magnetizing roasting iron tailings from eucalyptus chips are as follows:roasting temperature 650℃,adding 20%eucalyptus chips and roasting time 15min.At this time,magnetite concentrate with iron grade of 61.37%and iron recovery of 96.78%can be obtained.The optimal conditions for magnetizing roasting iron tailings with Chinese fir sawdust are as follows:roasting temperature 650℃,adding 15%Chinese fir sawdust and roasting time 15min.At this time,magnetite concentrate with iron grade of 61.33%and iron recovery of 96.74%is obtained.The optimal conditions for magnetizing roasting iron tailings with bamboo chips are as follows:roasting temperature 650℃,bamboo chips adding 20%,roasting time 20min,magnetite concentrate with iron grade of 61.32%and iron recovery of96.43%is obtained.The optimum conditions of iron tailings magnetized roasting with pine sawdust are as follows:roasting temperature 650℃,pine sawdust dosage 25%,roasting time15min,then magnetite concentrate with iron grade 61.25%and iron recovery 96.26%can be obtained.The magnetic roasting of plant biomass can effectively recover iron from iron tailings,which provides a green and feasible path for the treatment and utilization of iron tailings.